Project Summary Dr. Peter Sicinski's laboratory at the Dana-Farber Cancer Institute studies the functions of cell cycle proteins in normal development and in cancer. For the past 20 years, we have created many mouse knockout or knock-in strains including mice either lacking cyclins or CDKs, or expressing modified cyclins or CDKs. Using those mice, we delineated the requirement for cell cycle proteins during normal mouse development and in tumor formation/progression. As an expert in generating and analyzing genetically engineered mouse models, Dr. Yan Geng, the Research Specialist, has been leading the efforts in Dr. Sicinski's lab to create different cyclin/CDK mutant strains. Particularly, she has played a crucial role in the following areas: 1) design the genetic targeting strategies for knockout cyclin genes or knock-in mutations/tags into a cyclin or CDK gene locus; 2) supervise the technical processes for gene manipulation in embryonic stem (ES) cells and creating chimeric mice by blastocyst injection of ES cells; 3) design and perform the experiments using mouse tumor models including xenograft/allograft models. Currently, the Research Specialist is making a new mouse strain of conditional knockout Cdk19. Using this strain, we plan to investigate the effect of Cdk19 loss together with loss of cyclin C in T-cell leukemia. Combining Cdk19 knockout with cyclin C knockout, we hope to create a mouse model that faithfully mimicking human T-cell leukemia. The Research Specialist is also leading the study of G1 cyclins' function in cancer cell stemness. As we have found that G1 cyclins directly regulate the protein levels of pluripotency factors Oct4, Sox2 and Nanog not only in embryonic stem cells but also in glioblastoma tumor initiating cells, we will investigate whether decreasing the levels/activities of G1 cyclins would impact on the stemness of tumor cells. We will use a xenograft model to test whether knocking down the G1 cyclins will induce differentiation of glioblastoma cells thus to eliminate/reduce their potential to form tumors in vivo. Recently, we have found that cyclin D/CDK4/6 play roles in cancer immunity. Using tumor allograft mouse models, the Research Specialist is going to explore whether inhibition of cyclin D/CDK4/6 would enhance the efficacy of anti-immune checkpoint blockade in treatment of melanoma. We hope that this study will lead to a new combinational therapeutic strategy for melanoma patients.